1. Field of the Invention
The invention relates to the field of cementitious building materials and in particular concerns a siding clapboard comprising a mixture of sand, cement and a fibrous organic filler, which after forming to the shape of a plank which can be embossed with a simulated wood grain or can be smooth, is planed or routed to provide a cut bead along at least one edge.
2. Prior Art
Fiber reinforced hydraulically setting materials are durable and useful for building products such as exterior siding, roofing and the like. A slurry is mixed of one or more hydraulic binding agents such as portland cement, together with fine sand, water, a fibrous filler and optionally certain additives. The slurry is shaped to finished size and then cured. The resulting product is employed in a manner similar to other building materials such as wood or metal.
In a known forming process sometimes called the Hatschek process, a slurry as described is mixed, and with the aid of one or more dewatering sieves is deposited on an absorbent layer of felt. The felt is passed around a roller, and the dewatered slurry is transferred from the felt to the roller where it is built up in layers to the required product thickness. The roller can be smooth or can have ridges aligned substantially circumferentially, for imprinting the product with surface variations resembling the grain of a wooden clapboard. The layered slurry deposited on the roller is then subdivided into elongated panels or planks. After forming, the product is cured, for example for 24 hours, and then is treated with steam and pressure to complete hydration.
Examples of cementitious building products and methods for making them, including the addition of fiber and other materials either for reinforcement or for reducing product density and including details of Hatschek machines, are disclosed for example in the following U.S. patents, which are hereby incorporated:
U.S. Pat. No. 4,132,555--Barrable PA1 U.S. Pat. No. 4,133,928--Riley et al. PA1 U.S. Pat. No. 4,306,911--Gordon et al. PA1 U.S. Pat. No. 4,543,159--Johnson et al. PA1 U.S. Pat. No. 4,808,229--Arhelger PA1 U.S. Pat. No. 5,112,405--Sanchez PA1 U.S. Pat. No. 5,167,710--Leroux et al. PA1 U.S. Pat. No. 5,465,547--Jakel.
In addition to forming a surface wood grain pattern, the roller can have other variations in radial dimension for shaping the product. For example in clapboard siding, it is known to form a rounded decorative bead on one elongated edge by depressing the product thickness at the extreme edge and at a space from the edge. Likewise, to cause successive clapboards to lap more closely when installed, the edge opposite from the bead can be compressed in thickness. These thickness variations are formed in the uncured slurry, and due to settling and deformation of the wet slurry the resulting bead and thinned edge are relatively indistinct.